1. Field of the Invention
This invention relates to a copying method and apparatus using a recirculating document feeder, abbreviated as RDH, which enables exposure by sequentially taking out documents contained in a stacked state in means for containing.
2. Description of the Related Art
A copying machine is recently provided with a document feeder to feed documents sequentially to an exposure region in order to copy a plurality of sheet-like documents of a size efficiently. Also by repeating such copying operation a plurality of times, a plurality of sets of copies can be made arranged in the same order as documents. A typical prior art device for obtaining a plurality of copies is shown in U.S. Pat. No. 3,499,710 in FIG. 1 and U.S. Pat. No. 4,179,215 in FIG. 2.
FIG. 1 is a schematic sectional drawing of a document feeder 1 of the typical prior art. In the document feeder 1, document containers 4 and 5 are situated on both sides of a exposure region 3 of a copying machine main body 2. These document containers 4 and 5 are constructed in the same manner, and in the state shown in FIG. 1. A plurality of documents 7 are stacked and contained in main body 6 of the document container 4 which is on document feeding side. The documents 7 are pressed toward a bottom plate 6a of the main body 6 by spring force of a spring member 8a from above via a pressing plate 8. In the vicinity of the bottom plate 6a of a main body 6, a discharge port 9 is formed directed to the exposure region 3, and when a discharge roller 10 provided for the bottom plate 6 is driven, the documents in the bottommost layer are discharged through the discharge port 9. The documents 7 discharged through the discharge port 9 are sent onto a platen 13 composing the exposure region 3 through means for guiding 11, and transported to a predetermined exposure position suitable for the size of the documents 7 by means for transporting 12 realized by a transport belt or the like.
After the image of the documents 7 is copied onto a copy sheet, the documents 7 are thrown into an input port 15 of an other document container 5 on document containing side from the transporting means 12 through means for guiding 14. The input port 15 is formed above the level of the discharge port 9, and in the document container 5 on document containing side, the pressing plate 8 is displaced upward of the input port 15 against spring force of the spring member 8a by means for raising and lowering 16 realized by an electromagnetic plunger or the like.
Accordingly, the documents taken out from the bottom side of the document container 4 are thrown into the input port 15 of the document container 5 sequentially after exposure is made, therefore the documents 7 are contained in the document container 5 in the same order as when the documents were contained in the document container 4. When copying operation by the documents 7 in the document container 4 is all finished, the guiding means 11 connects the input port 15 of the document container 4 and the transporting means 12, the guiding means 14 connects the discharge port 9 of the document container 5 and the transporting means 12, further each pressing plate 8 in the document container 4 and 5 is raised and lowered respectively, and copying operation described above is made with the documents 7 from the document container 5. By moving the documents 7 back and forth in this way between the document container 4 and the document container 5, a necessary number of copies can be made in the same order as the documents 7.
On the other hand, the construction having the two document containers 4 and 5 occupies a large installation space, therefore a recirculating document feeder 21 is put into practical use wherein a single document container 22 is provided as shown in FIG. 2 and the documents 7 taken out of the document container 22 are returned to the document container 22. In this recirculating document feeder 21, the documents 7 are taken out sequentially from the bottommost layer through a discharge port formed on a bottom plate 23a of a main body 23 of the document container 22 by a discharge roller 24, transported onto a platen 27 of a copying machine body 26 by means for transporting 25 and exposed, sent from the transporting means 25 via means for guiding 28, then thrown in from above the main body 23 of the document container 22. The documents 7 are thus sequentially taken out from the bottommost layer and exposed, then the documents 7 are stacked in the uppermost layer, and such operation is repeated to make a plurality of sets of copies in the same order as that of the documents.
In the document feeding apparatus 1 constructed as described above, when copying of a few number of documents 7 is attempted in the same way as a large number of documents, feed of the documents for next copying operation can be restarted only after the documents are exposed and transported from the document container 4 on one side to the other side, i.e., the document container 5, then the guiding means 11 and 14 are driven to switch the discharge port 9 and the input port 15 as well as the raising and lowering means 16 is driven to vertically displace the pressing plate 8, which takes time.
Also in the recirculating document feeder 21 in FIG. 2, when the documents 7 are few, the guiding means 28 is sprung up as shown by a reference mark 28a, and the documents 7 are contained temporarily in the transporting means 25 without the documents 7 being returned to the document container 22. However, it still takes time since the length of a transporting path does not change much when the size of the documents 7 is small or the documents are small in number.